Fasciola hepatica is the species of parasitic flatworms that infects the liver of various mammals, including
humans. The disease caused by the organism is called Fascioliasis or Fasciolosis. It was first reported in
1379 by Jehan de Brie. However it wasn't until the 19th century that it role in humans was explained. Eggs
from Fasciola hepatica has also been found in mummies.The disease occurs worldwide and frequently in
sheep and cattle. Fasciola hepatica is found on every continent with nearly 180 million people at risk and an
estimated 2.4 million people already infected.
The shape of the parasite looks like a leaf, with one end tapering. Each individual parasite posseses ovaries
and testes, making them hermaphroditic and able to produce fertilized eggs. The organism attaches to bile
ducts with two powerful suckers on each end of its body. The bile ducts are where the mature flukes and
release eggs. The eggs are passed out in the host's feces. At temperatures over 10 degrees Celcius, the
eggs hatch and release miracidiae within two weeks. The hatchlings must find a Lymanaea snail host within
24 hours of hatching or they will die. After identifying a host snail, the hatchling Fasciola heptica burrow in
and begin developing into sporocyst. The germinal cells of the sporocyst develop into rediae which migrate
to the hepato-pancreas of the snail. The rediae then develop into cercariae which pass through the snail
into water. Cercariae encyst apon nearby plant matter for several months, where they can be ingested by a
mammal. Once a mammal ingests these metacercariae, the pH levels of the animals stomach allow the
Metacercariae to lose their shell. The cercariae freed from their cyst capsules, burrow through the stomach
lining and find their way to the liver. The immature flukes feed on the liver tissue for 6 to 8 weeks, causing
the symptoms of acute infection. At this stage the flukes move into the bile ducts where they mature and
release eggs, completing it's life cycle.
Susceptible animal hosts for Fasciola species include:
Domestic animals: cattle, sheep, pigs, buffaloes and donkeys;
Other domestic animals: horses, goats, dromedaries, camels and llamas; (hares, rabbits and rodents).
The acute phase of infection in humans is characterized by the migration of immature worms through the
liver; hemorrhage and inflammation of the liver can be severe, including fever, abdominal pain, respiratory
disturbances and skin rashes. The chronic phase starts when the worms move into the bile ducts; symptoms
are nonspecific and usually mild. However, progressive inflammation, leads to fibrosis and thickening of the
walls of the ducts and gallbladder that eventually may result in blockage due to the parasites, or their debris.
In this case, abdomen pain is a characteristic symptom. Chronic infections can lead to biliary cirrhosis with
scarring and fibrosis of the liver and growth deficiencies.
Antibody detection and ELISA tests are useful especially in the early invasive stages, when the eggs are not
yet apparent in stool samples. Examinations of stool samples alone are generally not adequate because
infected victims have important clinical presentations long before eggs are found in the stool. Immunological
tests such as the ELISA are based on detection of species-specific antibodies from blood plasma.
The drug of choice is triclabendazole with bithionol as an option. The drug works against both immature and
adult parasites, with high rates of cure. Adverse reactions to treatment are usually temporary and mild.